Magnetic recording mediums have been conventionally widely used in the field of cash cards, credit cards, ID cards, and the like. In magnetic recoding mediums, simple information, such as names of card owners and membership numbers, can be magnetically recorded, and identification of the card owners, etc. is performed on the basis of such information. However, in the magnetic recording mediums, the amount of information that can be recorded is limited. Furthermore, since magnetically recorded information can be easily read, there remains a concern with respect to security.
Recently, in view of prevention of leakage of personal information, there has been a demand for tightening security. IC cards including IC chips as recording mediums have been receiving attention for the sake of higher security and becoming mainstream. In particular, non-contact IC cards have been widely used in boarding systems, security systems, and the like, and widespread use of such IC cards is remarkable.
These cards are usually produced by thermal pressing of synthetic resins, such as plastics. When oriented PET substrates are vertically symmetrically placed and laminated on front and back surfaces of a core layer composed of a plurality of sheets interposed inside a card, in some cases, warpage may occur in the card after lamination with a press, giving rise to problems.
Such card warpage causes various defects. For example, moving characteristics may be affected by the warpage of the card when an initializer, a printer, or the like is used. It may become impossible to read information recorded in IC chips and magnetic stripes and to write information in these recording mediums. Furthermore, when a card is left to stand in high temperatures, the shape of an IC chip, etc. contained in the card may stand out, and as a result, moving characteristics may be affected when an initializer, a printer, or the like is used, as in the case of the card warpage described above. Consequently, there has been a need for a card in which card warpage due to thermal pressing is suppressed and degradation of the surface of the card is small, and which has excellent durability.
Accordingly, it is an object of the present invention to provide a synthetic resin card in which moving characteristics are improved when an initializer, a printer, or the like is used, and card warpage after pressing is reduced so that reading and writing from and in an IC chip, a magnetic stripe, or the like formed in the card can be performed satisfactorily, and which has excellent durability, and a method for producing such a synthetic resin card.